Wear side weave pattern of a composite forming fabric

ABSTRACT

A fabric for papermaking including a first layer side, a second layer side and at least one binder warp yarn pair. The first side layer, having a plurality of first weft yarns and a plurality of first warp yarns. The second side layer having a plurality of second weft yarns and a plurality of second warp yarns. The at least one binder warp yarn pair including a first binder warp yarn pair having a first binder warp yarn and a second binder warp yarn, the first side layer and the second side layer being bound by the first binder warp yarn pair. The first binder warp yarn and the second binder warp yarn exchanging the layer to which they are woven at exchange points. A knuckle is formed with the first binder warp yarn and an adjacent first warp yarn, a subsequent adjacent knuckle only being formed with the first binder warp yarn and an opposite adjacent first warp yarn.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compound papermaking fabrics. Morespecifically, the present invention relates to forming fabrics used inthe forming section of a papermaking machine.

2. Description of the Related Art

In the art of papermaking, multiple steps occur from the introduction ofa pulp slurry to the output of a finished paper product. The initialintroduction of the slurry is at the portion of a papermaking machineknown as the wet end. Here, the slurry, or fiber suspension, isinitially dewatered when the slurry is introduced onto a moving formingfabric, in the forming section of the papermaking machine. Varyingamounts of water is removed from the slurry through the forming fabric,resulting in the formation of a fibrous web on the surface of theforming fabric.

Forming fabrics address not only the dewatering of the slurry, but alsothe sheet formation, and therefore the sheet quality, resulting from theformation of the fibrous web. More specifically, the forming fabric mustsimultaneously control the rate of drainage while preventing fiber andother solid components contained in the slurry from passing through thefabric with the water. The role of the forming fabric also includesconveyance of the fibrous web to the press section of the papermakingmachine.

Additionally, if the drainage occurs to rapidly or too slowly, thequality of the fibrous web is reduced, and overall machine productionefficiency is reduced. Controlling drainage by way of fabric void volumeis one of the fabric design criteria.

Forming fabrics have been produced to meet the needs and requirements ofthe various papermaking machines for the various paper grades beingmanufactured. As the needs arises to increase production speed of thepapermaking machines and the quality of the paper being produced, theneed for improved paper machine clothing allowing for increaseproduction rates and improved quality resulted.

A twill pattern in woven fabrics is where a fabric is woven with apattern of diagonal ribs. The twill is typically made by passing theweft threads over one warp thread and then under two or more warpthreads. In this manner, in a twill weave, each warp or filling yarnfloats across two or more filling or warp yarns with a progression ofinterlacings by one to the right or left, which forms a distinctdiagonal line, or wale. A float is defined as the portion of yarn thatcrosses over two or more yarns from the opposite direction.

Twill weaves are generally designated as a fraction or ratio, forexample 2:1, where the numerator indicates the number of harnesses thatare raised, and the denominator indicates the number of harnesses thatare lowered.

A straight twill used in forming fabrics is well known, for example, inFIG. 1 a fabric 10 has a straight twill pattern 14. This fabric is proneto guide poorly and can lead to curling of the fabric edges. The twillpattern 14 can also “strike through,” or cause marking, and can causedrainage, or hydraulic marks on the web being formed on the fabric.Additionally, twill patterns also have the possibility of creating holeson the back of the fabric that are too large, resulting in drainagemarks.

U.S. Pat. No. 5,152,326 (Vöhringer '326) discloses a composite formingfabric having pairs of fabric borne warp binder yarns. However,Vöhringer '326 does not prevent diagonal marking of the web caused bythe diagonals present in the weave pattern, and unbroken diagonals arenot addressed.

U.S. Pat. No. 5,544,678 (Barrett '678) discloses different float lengthsachieved by using additional or intrinsic binders.

WO 2004/085740 to Ward discloses the use of varying the warp or weftratios between the top and bottom layers in order to break up the twillpattern. This break up of the twill pattern occurs only on the paperside surface of the fabric.

SUMMARY OF THE INVENTION

Accordingly, the present invention is for a fabric used in papermaking,and more particularly, as a forming fabric. In the preferred embodiment,the fabric is a composite multi-layer forming fabric whereby thediagonal twill is broken up on the wear side of the fabric. Also in apreferred embodiment, the warp paths are moved left and rightalternatively, disturbing the twill-type pattern.

One method of breaking up the twill line is to overlap adjacent warppairs. By offsetting an adjacent warp pair, a gap in the diagonal iscreated.

Another method of breaking up the twill line involves the use of fourdifferent floats on each warp yarn of three separate lengths. Fabricborn binders are used. In contrast, Barrett '678 discloses at least twolengths of float and additional or intrinsic binder.

In the first methods of breaking up the twill line, the warp pairs staytogether.

In another embodiment of the present invention, all of the warp yarnpairs change pairing to the left and to the right. There can also be a2:1 weft ratio or a 1:1 weft ratio.

For example, a fabric for papermaking can have a first side layer, thefirst side layer having a plurality of first weft yarns and a pluralityof first warp yarns; a second side layer, the second side layer having aplurality of second weft yarns and a plurality of second warp yarns; atleast one binder warp yarn pair; wherein the first side layer and thesecond side layer are bound by the binder warp yarn pair; wherein thebinder warp yarn pair is an exchange warp pair that exchanges atexchange points; wherein the binder warp yarn pair is woven in binderwarp pair yarn groups in a repeating pattern; and wherein each repeatingpattern of the binder warp yarn group forms a broken twill pattern.

Still further, the fabric has a first binder warp yarn pair having afirst warp yarn and a second warp yarn; wherein between a first exchangepoint and a second exchange point of the first warp binder yarn pair,the first warp yarn forming a knuckle on the first side layer, the firstside layer knuckle of the first warp yarn adjacent to one of the secondwarp yarn and an adjacent first side layer first warp yarns. In thismanner, one of the binder pairs yarns is moving from its' own pair tothe warp yarn on the left or right side of it, in an alternatingfashion. This breaks up the twill pattern, and gives the appearance thatone of the warp pair yarns is floating from left to right

It is also understood that there are no limitations to the paper gradesor former types where this invention can be applied. It is alsounderstood that the fabric can be woven utilizing either two or threewarp beams.

These and other features and advantages of this invention are describedin or are apparent from the following detailed description of thepreferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

The preferred embodiments of the present inventions will be described indetail, with reference to the following figures, wherein:

FIG. 1 is a plan view of the prior art;

FIG. 2 is a weave pattern of a prior art fabric having paired bottomwarps;

FIGS. 3A-3C show the individual weave pattern for each warp yarn of FIG.2;

FIG. 4 shows a weave pattern for a fabric having a 2:1 weft ratioarrangement according to an embodiment of the present invention;

FIGS. 5A-5C show the individual weave pattern for each warp yarn of FIG.4;

FIG. 6 shows a plan view of the fabric of FIG. 4;

FIG. 7 shows a weave pattern for a fabric having a 1:1 weft ratioarrangement according to another embodiment of the present invention;

FIGS. 8A-8C show the individual weave pattern for each warp yarn of FIG.7.

FIG. 9 shows a weave pattern for a fabric according to anotherembodiment of the present invention; and

FIGS. 10A-10C show the individual weave pattern for each warp yarn ofFIG. 9.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1, 2 and 3A-3C show the prior art. In FIG. 1, a plan view of thewear side of a papermaking forming fabric 10 having paired bottom warps12, and shows a diagonal twill 14.

In FIG. 2, the weave pattern for fabric 10 of the prior art havingpaired bottom warps 12 is shown. FIGS. 3A-3C show the individual weavepatterns for each warp yarn of FIG. 2. Alternate columns of FIG. 2represent warp yarns that are binder warp yarn pairs 12. For example,warp yarns marked 16 and 18 are a binder warp yarn pair 12. Warp yarns20 and 22 are only associated with either a top fabric 24 or a bottomfabric 26. Warps marked with an X 28 indicate that a top knuckle isformed. Boxes marked with a Y 30 and Z 32 are binder warp yarn pairs 34.The cross-hatched boxes 36 indicate where a warp exchange occurs betweenthe binder yarns 30 and 32 of binder warp yarn pair 34. The gray boxes38 are where bottom knuckles occur. In a warp pair group 34, when abinder warp yarn Y 30 occurs in a white box, the binder warp yarn Y 30is forming a top knuckle. When a binder warp yarn Y 30 is in a gray box38, the corresponding binder warp yarn Z 32 is forming a bottom knuckle.

The same is true of a warp pair group 34, when a binder warp yarn Z 32occurs in a white box, the binder warp yarn Z 32 is forming a topknuckle. When a binder warp yarn Z 32 is in a gray box 38, thecorresponding binder warp yarn Y 30 is forming a bottom knuckle.

FIG. 4 shows a weave pattern for a fabric 110 having a 2:1 weft ratioarrangement according to the present invention FIGS. 5A-5C show theindividual weave pattern for each warp yarn of FIG. 4; and FIG. 6 showsa plan view of the fabric of FIG. 4, with a broken twill pattern.

FIGS. 5A-5C depict a cross-sectional view of a triple layer fabric 110having a 2:1 weft ratio according to the present invention, fabricatedon a two beam loom. FIG. 4 depicts the forming side plan view of thesame fabric 110.

A first weft system 112 is shown above a second weft system 114. Eachweft system 112 and 114 is made up of a plurality of yarns 118, 120,122. First weft yarn 118 has a first yarn diameter, second weft yarn 120has a second yarn diameter, and third weft yarn 122 has a third yarndiameter. The first, second and third yarn diameters 118, 120, 122 canbe the same or different.

First weft system 112 and second weft systems 114 are bound together bya plurality of warp systems 124. FIGS. 5A-5C show six warp systems 124in a repeating pattern. Each warp system 124 has at least one warp yarn(illustrated in the example as having 2 warp yarns per warp system, suchas yarns 1 and 2), and each warp yarn system is woven as shown in FIGS.5A-5C.

The weft and warp yarn materials include, but are not limited to monofilament yarns, synthetic or polyester mono filament yarns, twisted monofilament yarns, twisted synthetic or twisted polyester or twistedpolyamide mono filament yarns, twisted multi-filament yarns, twistedsynthetic or twisted polyester multi-filament yarns, and others. Variousyarn profiles can be employed, including but not limited to yarns havinga circular cross sectional shape with one or more diameters, or othercross sectional shapes, for example, non-round cross sectional shapessuch as oval, or a polygonal cross sectional shapes, for examplediamond, square, pentagonal, hexagonal, septagonal, octagonal, and soforth, or any other shape that the yarns may be fabricated into.

First warp yarn 126 binds the top or first weft system 112. Second warpyarn 130 binds second weft system 114. Warp yarns 132 and 134 form whatis called an exchange warp. An exchange warp is, for example, when onemember of a pair of warp yarns 132 and 134 is weaving with first weftsystem 112, and the other member of the pair of warp yarns 132 and 134is weaving with second weft system 114. Stated differently, an exchangewarp allows for one warp yarn of a pair of warp yarns to weave inalternate fashion such that when the warp yarn 132 is weaving with firstweft system 132, the warp yarn 134 is not weaving with first weft system112, and both the warp yarn 132 and warp yarn 134 are not weaving withthe same weft system at the same time.

In the present invention, while depicting a plurality of warp systems124, some yarns of the warp systems form exchange warp pairs and some ofthe warp systems do not form exchange warp pairs. For example, the firstwarp yarn 126 and warp yarn 130 form the first warp system 128, which isnot an exchange warp pair. In contrast, warp yarn 132 and warp yarn 134do form an exchange warp pair. Accordingly, when warp yarn 132 crosseswarp yarn 134 an exchange warp is formed.

FIG. 4 depicts the forming side plan view of the triple layer fabric 110having a 2:1 weft ratio of the present invention. In this example, itcan be readily seen that warp yarns 132 and 134 form a warp system, andtherefore a warp pair that forms an exchange warp. The warp yarn systemsare independent from one another and each have a mesh density that isindependent. In FIG. 4 the ‘X’ notation marks where a knuckle is formedby a warp yarn that is woven exclusively with a weft yarn closest to theforming side. The ‘Y’ indicates where a knuckle is formed by a warp yarnthat is woven with weft yarns on both the forming and the wear side ofthe fabric. The ‘Z’ indicates where a knuckle is formed on the paperside of the fabric by another warp yarn and exchanges it's weavingbetween the weft yarns of both the paper side and wear side of fabric10. The shaded boxes indicate where a knuckle is formed by a warp yarnthat is woven exclusively with the weft yarns on the wear side of thefabric 10. The cross-slashed boxes indicate where warp yarns exchangethe layer of weft yarns each warp yarn is individually woven with. Sincethe invention is directed to triple layer of fabric, the side shown isthe paper side with the wear side being on opposite side as indicated inFIG. 4.

The warp yarns can have different diameters, for example warp yarns 126,130, 132 and 134 can each have a different diameter. The warp yarns andthe weft yarns can include monofilament yarns and twisted pair yarns.

This pattern repeats throughout the forming side plan view. Accordingly,the views in FIGS. 4 and 5A-5C show a pattern. That is repeated every 36weft yarns in the machine direction and every 12 warp yarns in thecross-machine direction, resulting in a broken twill pattern.

FIGS. 7 and 8A-C depict a cross-sectional view of a triple layer fabric210 having a 1:1 weft ratio according to another embodiment of thepresent invention. FIG. 7 depicts the forming or paper side plan view ofthe triple layer fabric. As in FIGS. 4 and 5A-5C, the second set of warpyarns form an exchange warp pair. The difference is that the warp yarnshave a different weave pattern.

FIGS. 8A-8C depict a cross-sectional view of a triple layer fabrichaving a 1:1 weft ratio. Twenty-four warp yarns and forty-eight weftyarns are shown with the designations of the boxes of FIG. 7 being thesame as for FIG. 4.

FIGS. 9 and 10A-C depict a cross-sectional view of a triple layer fabric310 according to another embodiment of the present invention. FIG. 9depicts the forming or paper side plan view of the triple layer fabric.The first, third, fifth, seventh, ninth and eleventh set of warp yarnseach form an exchange warp pair. The warp yarns again have a differentweave pattern from those described above.

FIGS. 10A-C depict a cross-sectional view of the fabric illustrated inFIG. 9. Twenty-four warp yarns and thirty-six weft yarns are shown withthe designations of the boxes of FIG. 9 being the same as those forFIGS. 4 and 7 as described above.

On at least one side of the fabric, knuckles are formed by the weavingof a binder warp yarn with alternating adjacent non-binder warp yarns.This causes the knuckles to alternate back and forth as can be seen bythe shaded blocks of FIGS. 4, 7 and 9. This is in contrast to the priorart as illustrate in FIG. 2 where the knuckles do not alternate. Thispattern continues as the yarns of the binder warp yarn pair exchangetheir weaving with the first and second layers of the fabric. As can beseen in the figures in some cases no more than four knuckles are formedin this manner between exchange points. In other patterns of the presentinvention no more than two knuckles are formed between exchange points.

The invention as it has been described can be fabricated on a three beamloom. Likewise, the triple layer fabric of the present invention canalso be fabricated on a four beam loom. Use of four beams could resultin similar fabrics, with the addition of at least one of a top onlywarp, a bottom only warp, a bottom warp that binds at the second weftsystem, and a top pair that bind with the second weft system.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

1. A fabric for papermaking, comprising: a first side layer, having aplurality of first weft yarns and a plurality of first warp yarns; asecond side layer having a plurality of second weft yarns and aplurality of second warp yarns; and at least one binder warp yarn pairincluding a first binder warp yarn pair having a first binder warp yarnand a second binder warp yarn, the first side layer and the second sidelayer being bound by the first binder warp yarn pair, the first binderwarp yarn and the second binder warp yarn exchanging the layer to whichthey are woven at exchange points, a knuckle being formed with the firstbinder warp yarn and an adjacent first warp yarn, a subsequent adjacentknuckle only being formed with the first binder warp yarn and anopposite adjacent first warp yarn.
 2. The fabric for papermaking ofclaim 1, wherein no more than four knuckles are formed between exchangepoints on the first layer along the binder warp yarn pair.
 3. The fabricfor papermaking of claim 1, wherein no more than two knuckles are formedbetween exchange points on the first layer along the binder warp yarnpair.
 4. The fabric for papermaking of claim 1, wherein the knuckle is afirst knuckle, the subsequent adjacent knuckle is a second knuckle, thesecond knuckle being the last knuckle prior to an exchange point, afterthe exchange point the second binder yarn forms a third knuckle with theadjacent first warp yarn.
 5. The fabric for papermaking of claim 4,wherein the second binder yarn forms a fourth knuckle with the oppositeadjacent warp yarn.
 6. The fabric for papermaking of claim 5, wherein onthe first layer side the at least one binder warp pair only hasalternating knuckles in a repeating pattern.
 7. The fabric forpapermaking of claim 1, wherein at least one of the plurality of firstweft yarns and the plurality of second weft yarns include a first yarnhaving a first diameter a second yarn having a second diameter and athird yarn having a third diameter.
 8. The fabric for papermaking ofclaim 7, wherein at least one of the plurality of first warp yarns, theplurality of second warp yarns and the at least one binder warp yarnpair include a warp yarn having a diameter different than the firstdiameter, the second diameter and the third diameter.
 9. The fabric forpapermaking of claim 1, wherein the warp yarn and the weft yarns includeat least one of a monofilament yarn and a twisted pair yarn.
 10. Thefabric for papermaking of claim 1, wherein the fabric is fabricatedusing a loom having at least three warp beams.